Even-loading DPF and regeneration thereof

Abstract

A motor-vehicle engine system comprises an envelope configured to transmit exhaust. The envelope encloses a first array of filtration cells downstream of a second array of filtration cells. The system further comprises a fuel injector configured to increase a temperature in the envelope when soot is evenly distributed between the first and second arrays in order to address thermal gradients.

The invention claimed is: 
     
       1. A system comprising:
 an envelope configured to transmit exhaust, the envelope enclosing a first array of filtration cells downstream of a second array of filtration cells, each cell of the first array having one open end and one closed end, each cell of the second array having one or two open ends; 
 a fuel injector; and 
 a computer readable storage medium in an electronic control system including code configured to trigger a temperature increase in the envelope via the fuel injector when soot is evenly distributed between the first and second arrays. 
 
     
     
       2. The system of  claim 1  further comprising a backpressure sensor coupled in an exhaust conduit upstream of the envelope, wherein the code in the electronic control system is further configured to receive a signal from the backpressure sensor. 
     
     
       3. The system of  claim 2  further comprising a temperature sensor coupled in an exhaust conduit downstream of the envelope, wherein the code in the electronic control system is further configured to receive a signal from the temperature sensor. 
     
     
       4. The system of  claim 1 , wherein each cell of the second array has an open end for receiving an exhaust flow opposite the open or closed end. 
     
     
       5. The system of  claim 1 , wherein each cell of the first and second arrays includes an exhaust-permeable partition which separates that cell from neighboring cells. 
     
     
       6. The system of  claim 5 , wherein the exhaust-permeable partition includes a catalyst wash coat. 
     
     
       7. The system of  claim 6 , wherein the catalyst wash coat includes a NO x  reduction catalyst. 
     
     
       8. The system of  claim 1 , wherein the envelope also encloses a radial diffusion zone arranged between the first and second arrays. 
     
     
       9. The system of  claim 8 , wherein the radial diffusion zone comprises a void space that separates the first array from the second array. 
     
     
       10. The system of  claim 1 , wherein some cells of the second array have a closed end opposite the first array and the rest of the cells of the second array have an open end opposite the first array, and wherein the cells with a closed end opposite the first array admit of a larger flow area than the cells with an open end opposite the first array. 
     
     
       11. The system of  claim 10 , wherein each cell with an open end opposite the first array includes a flow restrictor. 
     
     
       12. A method for removing soot from motor-vehicle exhaust using a regenerable soot filter, the filter comprising a first array of filtration cells enclosed in an envelope downstream of a second array of filtration cells, the method comprising:
 trapping the soot in the first array at a first rate; 
 trapping soot in the second array at a second rate, the second rate decreasing faster than the first rate; and 
 increasing a temperature in the envelope to oxidize the soot when the soot is evenly distributed between the first and second arrays. 
 
     
     
       13. The method of  claim 12 , wherein each cell of the first array has one open end and one closed end and is oriented such that the open end is adjacent one or more closed ends of neighboring cells of the first array. 
     
     
       14. The method of  claim 12 , wherein each cell of the second array has an open or closed end opposite the first array and is oriented such that each closed end is adjacent one or more open ends of neighboring cells of the second array. 
     
     
       15. The method of  claim 12  further comprising radially diffusing the exhaust between the first and second arrays. 
     
     
       16. The method of  claim 12 , wherein increasing the temperature in the envelope comprises sensing a backpressure upstream of the filter and increasing the temperature when the backpressure exceeds a threshold. 
     
     
       17. The method of  claim 12 , wherein increasing the temperature in the envelope comprises sensing a temperature downstream of the filter and varying one or more of a fuel-injection amount and a fuel injection timing to exert closed-loop control of the sensed temperature. 
     
     
       18. A method for operating a soot filter comprising a first array of filtration cells enclosed in an envelope downstream of a second array of filtration cells, comprising:
 trapping soot in the first array at a first rate while, 
 trapping soot in the second array at a second rate decreasing faster than the first rate; and 
 increasing an envelope temperature to oxidize the soot when the soot is evenly distributed between the first and second arrays.